The present invention relates to systems and methods for facilitating material separation (sedimentation) through passive means. More particularly, the present invention relates to the use of cyclonic flow and the differences in the density of the solid and liquid components for separation.
Solids are typically classified by using three different criteria, size, state and chemical characteristic. In addition, solids may be differentiate by one of four size categories:
Dissolved Solids are defined by having a size of less than 10xe2x88x926 mm and are composed of ions and molecules that are present in the solution.
Colloidal Solids are defined by having a diameter between about 10xe2x88x923 to 10xe2x88x926 mm. These solids include many fine clay particles, virus and some bacteria.
Suspended Solids (non-filtrable) are defined by having a size greater than about 10xe2x88x923 mm and can be trapped by a 1.2 micron filter.
Settleable Solids are a subsection of suspended solids that will settle out of solution, when left un-agitated, for instance, in an Imhoff cone, for about one hour.
Solids can be removed from solution in many ways. One of the most common is physical filtration. Physical filtration includes the use of filters, such as screens, bags, pleated cartridges, etc., and the use of gravity separators, such as sedimentation, centrifuging, and hyrodcloning. Gravity separators are normally much more passive than screen filters, but normally only remove large particles and are subject to changes in efficiency due to solid and water characteristics. Despite this, gravity separators have been utilized worldwide in the primary treatment process of wastewater.
The removal of suspended and settleable solids from solution by permitting these solids to settle by gravity is called sedimentation. Sedimentation is often a primary treatment method for wastewater containing solids, since it is a low energy, passive filtration process that can be easily harnessed. Sedimentation can take place anywhere there is a change in water velocity or hydraulic retention time (HRT), and has been accomplished by the use of a variety of devices, for instance, hydroclones, swirl separators and deceleration basins. Such devices can be as simple as a pipe increasing from, for example, 6 cm in diameter to 12 cm in diameter, to create a larger cross sectional area with decreasing the flow velocity, which can result in an increased HRT.
Present technology has employed sedimentation in combination with centrifugal force to aid in the primary treatment of suspended and settleable solids. For example, by employing a centrifugal force, the spinning motion generated therefrom can be used to increase the gravitational force on the particles to increase the settling rates.
The present invention provides, in accordance with one embodiment, a device for separating solids from a fluid environment. The device, in an embodiment, includes a housing having a substantially cylindrical upper portion and a substantially conical lower portion configured to collect solids which have been separated from the fluid environment. The device further includes a chamber at an intersection between the cylindrical upper portion and the conical lower portion for introducing a cyclonic flow pattern into the housing. An inlet may be provided on the chamber to introduce a suspension of solids into the housing. In one embodiment, the inlet may be positioned in tangential communication with the chamber to impart a cyclonic within the chamber. The tangential position of the inlet relative to the chamber permits the fluid introduced through the inlet to follow a cyclonic path within the chamber. A drain port may be placed at an apex of the conical portion through which separated solids can be removed. The device also include an overflow weir positioned about the cylindrical upper portion to collect fluid substantially free of solids as the fluid rises from within the housing. An weir outlet may be provided, so as to direct the fluid within the overflow weir therefrom.
The present invention also provides a method for removing solids from a fluid environment. The method includes generating a uniform cyclonic flow pattern from a fluid environment having a suspension of solids. Next, the cyclonic flow pattern may distributed into a conical volume, such that the flow pattern decreases in velocity. Thereafter, as the flow pattern rises within the conical volume, solids in suspension may be permitted to separate from the fluid and to settle towards an apex of the conical volume, leaving the ascending fluid substantially free of solids. The settling of the solids can occur by allowing the ascending fluid to move at a velocity that is less than the velocity of the settling solids. The ascending fluid that is substantially free of solids can be then removed, while the settled solids, accumulated at the apex of the conical volume, can subsequently be drained.